DESCRIPTION (Applicant's abstract verbatim): The cooling of high-field super conducting magnets adds an additional component to the operating cost of MRI: the cost of replenishing the liquid helium cryogen that is continuously lost to boil-off. Chesapeake Cryogenics proposes to construct a recondenser that will liquefy helium gas, enabling its re-use, and thereby lowering the total operating cost of MRI. The recondenser borrows heavily on a new, patented refrigeration scheme called the BOREAS cycle. As well as using proven refrigeration cycles and components to achieve its goal of 2 watts at 4K. Its advantages include low vibration, the capability to move much of the mechanism up to 60 feet from the MRI unit, and lower power usage than other refrigerator-types. The proposed recondenser will eliminate the need for liquid helium replenishment in existing MRI systems with a minimum of modifications to the MRI unit. In the Phase I project Chesapeake Cryogenics has established the feasibility of a recondenser through design, simulation and experimentation of the recondenser performance. The resulting recondenser will be retrofitable on a wide variety of MRI magnet systems both stationary and mobile and has the design flexibility to meet the cryogenic needs of most units now in service world wide. In Phase II Chesapeake Cryogenics will construct the complete optimized recondenser and demonstrate its performance on a commercial MRI unit. PROPOSED COMMERCIAL APPLICATION: The proposed liquid helium recondenser will lower the operating cost of high-field MRI. It will also enable new MRI systems that employ superconducting magnets, but do not require the replenishment of any cryogens.